1. Field of the Invention
The present invention relates to an apparatus for controlling the position of a looper, as well as speeds of a steel plate passed therethrough, the looper being a device for continuously sending into or taking out of a central processing unit for continuous processing of steel plate or the like made endless, for example, by welding.
2. Description of the Prior Art
In equipment for continuous processing of steel plates, in general, the steel plate in a predetermined length wound around a reel is rewound as the reel is rotated and supplied to a central processing unit to be given such processing as rolling, surface treatment, or the like, and the steel plate, after being processed as desired in the central processing unit, is again wound around a reel and cut to a predetermined length and thus made into a product or half-finished product in a roll form.
Among the principal constituents of such continuous processing equipment, there is at first provided an entrance-side section including a pay-off reel assembly consisting of a plurality of reels around which steel plates of a predetermined length are wound in a roll form and a welder for joining the tail end of a steel plate supplied from one of the mentioned reels and the front end of a steel plate from another reel. And then, there is provided an entrance-side looper for feeding a steel plate continuously supplied from the above mentioned entrance-side section to the following sections such that the steel plate weaves its way through a plurality of rollers arranged therein substantially in two lines. As the section next to the entrance-side looper, there is provided a central section including the central processing unit for specified continuous processing of the steel plate, such as rolling, surface treatment, or the like. The continuous steel plate given the specific processing in the central processing unit is taken out of the central section by means of an exit-side looper of the structure corresponding to the above mentioned entrance-side looper. The thus taken out continuous steel plate is wound around a reel in a predetermined quantity in the following exit-side section and made into a product or half-finished product in a roll form. The exit-side section includes a tension reel assembly consisting of a plurality of reels around each of which a predetermined quantity of the steel plate is to be rolled and a shear for cutting the continuous steel plate wound around each of the individual reels of the tension reel assembly in a predetermined quantity.
In the continuous processing equipment for steel plates of the above described structure, since the steel plate is continuously supplied to the equipment while such operations are performed thereon as the welding by the welder in the entrace-side section, processing by the central processing unit in the central section, and cutting by the shear in the exit-side section, it is required that the traveling speed of the continuous steel plate be controlled through regulation of the position of rollers arranged in one line out of two lines constituting the entrance-side and exit-side loopers.
Therefore, there has been proposed a speed control apparatus as shown in the block diagram of FIG. 1 (Japanese Patent Laid-open No. 59-177246/1984). This apparatus is arranged based upon the following fundamental equations: ##EQU1## where V.sub.E --Entrance-side speed
V.sub.C --Exit-side speed PA1 .alpha.--Rate of acceleration/deceleration on the entrance side PA1 L.sub.SY --Looper synchronization set position PA1 L.sub.P --Present looper position.
In FIG. 1, the entrance-side speed (looper entrance-side speed) V.sub.E is measured by the entrance-side speed measuring circuit 13, the central speed (looper exit-side speed) V.sub.C is measured by the central speed measuring circuit 12, and the present looper position L.sub.P is measured by the looper position measuring circuit 14. The central speed (looper exit-side speed) V.sub.C, entrance-side speed V.sub.E, and the present looper position L.sub.P measured by these measuring circuits 12, 13, and 14 are input to the looper synchronized position control circuit 15, and in this circuit 15, the looper synchronization set position is determined through predetermined calculation. According to the thus determined looper synchronization set position, an entrance-side set speed V.sub.E REF is output from the entrance-side speed normalizing circuit 11 and the steel plate supplying speed of the entrance-side looper is thus controlled.
The prior art speed control apparatus operates as indicated in the time chart of FIG. 2. Namely, in the case where the looper entrance-side speed V.sub.E and the looper exit-side speed V.sub.C are different, the speed control is exercised such that the looper changes its position and deceleration is started at a predetermined rate of deceleration (e, FIG. 2), and after the decelerating operation has been performed for a predetermined period of time (T.sub.2, FIG. 2), the looper exit-side speed V.sub.C and the entrance speed V.sub.E are put in synchronism (d, FIG. 2).
According to the prior art speed control apparatus as described above, however, in the middle of the decelerating process of the looper entrance-side speed V.sub.E after the same has been started to be decelerated (e, FIG. 2) in order that the same may be synchronized with the looper exit-side speed V.sub.C, if, for example, the looper exit-side speed V.sub.C is accelerated, it took a considerably long period of time to achieve the synchronization between both the speeds and it was a problem in the prior art. More particularly, if the looper exit-side speed V.sub.C is accelerated at the point a in FIG. 2, the entrance-side speed V.sub.E is decelerated until it is brought to the point (b, FIG. 2) where the same becomes equal to the exit-side speed V.sub.C which is at the speed-increasing inclination, but, from this point on, the entrance-side speed V.sub.E becomes to be accelerated, not continued to be decelerated. Therefore, although the syncrhonization should have been completed within a predetermined period of time T.sub.2, it is caused by the change in the middle of the course to exceed the predetermined period of time T.sub.2 and require the period of time T.sub.1 down to the point (c, FIG. 2) where the entrance-side speed V.sub.E and the exit-side speed V.sub.C are put in synchronization. Thus, in the prior art speed control apparatus in which the entrance-side speed V.sub.E was accelerated or decelerated to come in synchronization with the exit-side speed at the constant rate of acceleration/deceleration .alpha., if there occurred some change in the exit-side speed V.sub.C, the entrance-side speed V.sub.E was first accelerated to become faster than the synchronous speed and then decelerated according to the rate of acceleration/deceleration .alpha., and so, the speed control was retarded and it took a long time before the control is achieved.